Oh man. I totally forgot to post here where nobody will read it about my
tuner app. I made this for myself a couple of years ago and finally polished it up just enough to put it on the App Store this spring. It’s basically just a visualizer that compares what it hears to the configured reference tones (i.e., the notes you’re tuning to) which makes it much more responsive than a pitch-detecting tuner.
It’s free, but I also added a special cosmetic-only feature as a 99 cent in-app purchase, just to see how many people would “tip” me. So far it’s paid for my annual developer membership, so that’s nice.